The present invention relates to multi-cylinder Diesel engines of the type employing variably actuated valves.
In American patent U.S. Pat. No. 6,237,551, the Applicant has already proposed an engine of this type including:                two inlet valves and two exhaust valves for each cylinder, each equipped with respective elastic means of return that push the valve towards its closed position, for controlling the respective inlet and exhaust ports,        at least one camshaft for operating the inlet and exhaust valves of the engine's cylinders via respective valve lifters, each inlet valve and the two exhaust valves being controlled by a respective cam of the said camshaft,        in which each of the said valve lifters commands the respective inlet or exhaust valve against the action of the said elastic means of return via the interposition of hydraulic means including a pressurized fluid chamber.        the pressurized fluid chamber associated with each inlet valve or with the two exhaust valves being suitable for connection via a solenoid valve to a discharge channel, for the purposes of decoupling the valve from its respective valve lifter and provoking rapid closure of the valve under the effect of the elastic means of return,        electronic means of control for controlling each solenoid valve for varying the time and travel of the respective inlet or exhaust valve according to one or more of the engine's operating parameters,        in which each cam on the engine camshaft has a profile such that it tends to provoke the opening of the respective inlet valve or respective exhaust valves that it controls, not only during the conventional opening phase of the engine's normal operating cycle, but also in certain additional phases of the cycle,        in which the said electronic means of control are capable of provoking the opening of each solenoid valve to maintain the respective inlet valve or the respective exhaust valves closed during the above-mentioned conventional phase and/or during one or more of the said additional phases in which the respective cam would tend to provoke the opening of the valve, in consequence of which the engine can be made to selectively run according to different modes of operation controlled by the said solenoid valves, and        in which the profile of the cam controlling the exhaust valves is such as to cause an additional opening phase of the exhaust valves substantially during the final part of the induction phase, thereby realizing an operating cycle of the so-called “post-charging” type, where, due to excess pressure in the inlet port, the opening of the exhaust valves during the final part of the induction phase causes fresh air to first flow directly from the inlet port to the exhaust port, while successively, following the increase in pressure in the exhaust port, part of the air returns from the exhaust port, entering the cylinder by exploiting the excess pressure in the exhaust port, thereby improving cylinder replenishment.        